Chapter 5 Introducing SDN Control in MPLS Networks - High ...

174 CHAPTER 5. INTRODUCING SDN CONTROL IN MPLS NETWORKSIn this chapter, we first discuss MPLS in relation to the flow and map abstractions.We show how flows in MPLS are close to the description of the flow-abstraction in theSDN context. And we also show how maps in MPLS networks are not quite the same asmaps in SDN. But more importantly, we discuss how the map-abstraction is missing inMPLS. Accordingly all the benefits of the map-abstraction in terms of simplicity,extensibility and global-optimization are also missing in MPLS networks. We giveexamples of the benefits of introducing the map abstraction in MPLS networks.To demonstrate that our approach can replicate services provided by MPLS today, wediscuss a prototype implementation of MPLS based traffic engineering (MPLS-TE).There are two goals of this prototype: First, we show the simplicity of our approachcompared to the existing MPLS control plane, by implementing nearly all the featuresthat are part of MPLS-TE in just 4500 lines of code, compared with an estimated100,000+ lines of code from a more traditional approach; and second, we show how theimplementation of features can be made different from the traditional implementation inways that either, greatly simplifies the feature, or provides a feature that MPLS-TEcannot provide.Finally, we discuss how introducing the map-abstraction in MPLS networks fits wellwith our unified-control architecture for packet and circuit networks; a fact that makesour control architecture ideal for multi-layer networks.5.1 MPLS Usage ModelsThere are two basic usage-models for MPLS, which correspond to the two services thatMPLS provides – VPNs and TE. VPNs use what can best be described as a datagrammodel, similar to IP datagram forwarding. On the other hand, TE uses a flow-basedmodel. Both models can and do exist simultaneously in today’s networks. In this section,we briefly discuss these models. Note that the terminology used for naming the models is